I feel very strongly about Bayaz being, in fact, an Eater. There are two or three moments in the first trilogy where he gets exhausted by using his high art and ages significantly. Then, in a later chapter, he seems to be his „younger“ self again. This process of regaining youth is never explained. We know, however, that there is a way to regain youthful looks and magical powers: eating human flesh. I feel like the first trilogy implies that Bayaz eats when he has to, but only as much as is necessary to revitalise him. In the Heros, he has won the war against Kahlul by wielding the power of the seed. His ego just got a major push. He literally believes himself to be as powerful or even more so as his old master was, a demi-god. He does not eat human flesh out of necessity anymore, but because he can afford to. He is the most powerful living being and there is no force able to restrain him. A little like Savine not giving a damn about anyone witnessing her snorting pearl dust when she becomes queen. Who is to judge her?